I've come to the conclusion that what we perceive as the advantage of light wheels and tires is really the mentioned agility factor and not the individual accelerations of each pedal stroke. Thought differently about that as recent as a couple months ago, but having seen a few real world tests of exactly what IAB references (weight on frame vs wheels) it consistently doesn't effect times on flats and very minimally on grades (so minimally as to be hardly measurable). The consensus of the sources is that aero makes more of a difference.

I personally think that light wheels are "fast" by way of less wind resistance from fewer spokes, and light tires are "fast" by way of lower rolling resistance generally due to more flexible sidewalls (usually also higher TPI casings). Perhaps that's why sources like Zinn argue that light weight matters. It does I think, but seemingly zero measurable benefits for "lightness" itself in any controlled situation.

Going up hills seems the greatest of the common roadie acceleration situations. Gravity slows you down more between pedal strokes than on a flat road. Even there, the controlled tests show very minor to no benefits of the "easier acceleration factor" due to the light wheels.